The present invention generally relates to a data record/reproduction system for reading out data from a card or writing data into the card. More particularly, the present invention relates to a card carrier in use with an optical data record/reproduction system using an optical card as a card.
There is a proposal of an optical card as a recording medium for an optical data record/reproduction system of the type in which a light beam (laser beam) is used for the read/write of data.
In the optical data record/reproduction system, to write data into the optical card or read out data from the card, the card must be moved relative to an optical read/write head. In this respect, a card carrier 1 as perspectively illustrated in FIG. 7 has been proposed for the optical data record/reproduction system using an optical card.
The card carrier 1 is made up of a pair of parallel guide rods 2 and 3 which are spaced from each other by a predetermined distance, and a table 4 reciprocatingly moving along the paired guide rods 2 and 3. An optical card 5 is set to and supported by the table 4, and the card, together with the table 4, is reciprocatingly moved in the direction of arrow A.
A pair of parallel support members 6 and 7 are fastened to the lower surface of the table 4. The support member 6 has a pair of through holes 6a through which the guide rods 2 and 3 are passed. Similarly, the support member 7 has a pair of through holes 7a through which the same rods are passed.
The table 4 is reciprocatingly moved in the guide rod extending direction (of arrow A) by a table drive means 14, which is constructed with a rack 11 fixed to the lower surface of the table 4, a pinion 12 in mesh with the rack 11, a motor 13 to drive the pinion 12, and the like.
An optical head 8 is arranged in parallel to a phantom plane containing the pair of guide rods 2 and 3 of the table 4. The head 8 is further supported by a guide rod 9 oriented orthogonal to the extension of the guide rods 2 and 3. The optical head 8 is reciprocatingly moved along the guide rod 9 in the direction (of arrow B) orthogonal to the moving direction of the table 4, by means of a drive means constructed with a worm 10.
The optical head 8 scans a memory area 5a on the upper surface of the optical card 5 through the combination of the reciprocating motions of the table 4 and the head 8 whose directions are orthogonal to each other, thereby to read out data from and write data into the memory area 5a.
A record width (track pitch) of a data unit (pit) of the data to be recorded in the record area 5a of the card 5 is very narrow, approximately 10 to 12 .mu.m. A high accuracy of positioning the table 4 relative to the head 8 that is performed in read and write modes, is required.
In the card carrier 1 as mentioned above, as shown in FIG. 8 showing a sectional view of a key portion of the mechanism of FIG. 7, the guide rods 2 and 3 are passed through those holes 6a and 7a and must be smoothly moved therethrough. To this end, a diameter L of each of the through holes 6a and 7a of the support members 6 and 7, which are fixed to the lower surface of the table 4, is slightly larger than a diameter "l" of each of the guide rods 2 and 3, within a tolerable range. Therefore, a play due to the diameter difference essentially exists between the holes 6a and 7a and the guide rods 2 and 3.
When a vibration externally applied and a vibration originating from a drive system are applied to the card carrier involving such a play in the transport mechanism including the guide rods 2 and 3 and the through holes 6a and 7a, the table 4 is possibly tilted vertically with respect to the extension of the guide rods 2 and 3 within a range of the play, as shown in FIGS. 9 and 10.
Further, the table 4 may be tilted horizontally with respect to the extension of the guide rods 2 and 3 within a range of the play, as shown in FIGS. 11 and 12 showing sectional views of a key portion of the mechanism of FIG. 7. Those tilts of the table 4 degrades an accuracy of the relative positioning of the table 4 and the head 8, thereby to make it impossible for the head 8 to exactly read out data from and write data into the memory area.
In the card carrier 1 shown in FIG. 7, the table drive means 14 is constructed with a rack-pinion mechanism inherently suffering from a backlash, which includes the rack 11 and the pinion 12. Because of the backlash, a vibration tends to occur in the table drive means 14 particularly when the motor 13 starts and stops. A vibration generated in the drive means 14 is transferred through the rack 11 to the table 4. Consequently, the relative positioning accuracy of the table 4 and the head 8 is degraded, thereby to make it impossible for the head 8 to exactly read out data from and write data into the memory area.